High temperature resistant gaskets are used to provide a seal against combustion gases at elevated temperatures. Such gaskets include cylinder head gaskets, exhaust manifold gaskets and turbocharger gaskets. In particular, cylinder head gaskets typically extend around cylinder bores to provide a combustion seal, maintaining the high temperature gases of combustion within the cylinder bore. The gasket bears the load from a bolted connection of the engine block and cylinder head components and relies upon that load to provide a seal.
It is known to provide cylinder head gaskets with a single flange positioned adjacent a cylinder bore opening formed in a body of the gasket. The flange is generally U-shaped in cross-section, having a central web portion separating upper and lower legs that extend continuously around the inner peripheral boundary of the cylinder bore opening and engage upper and lower surfaces of the gasket body.
Typically, an annular sealing element, such as a steel fire ring, having a generally circular cross-section is disposed within a trough defined by the U-shaped cross-section of the flange. The fire ring forms a seal that helps protect the gasket body from the deleterious effects of the combustion environment. Metals used in a fire ring include 1008 low carbon steel and 304 stainless steel.
A portion of the clamping force resulting from the bolting of the mating components is applied to the fire ring. The force is concentrated at the point of contact, plastically deforming the ring's circumference to effectively seal out combustion gases. However, because of the plastic deformation, existing fire rings have low elastic recovery which affects the gasket in the area adjacent to the rings. Fire rings made from soft metals such as copper typically have even less elastic recovery than those rings made from steel because they are readily plastically deformed. However, soft metal fire rings do have excellent initial conformity. Further, known fire rings are subject to thermal crushing which produces additional plastic deformation that occurs at high temperature operation during the life of the fire rings. Thus, the limited elastic recovery of the fire rings is further reduced over time.
The disadvantages of known fire rings also affect the performance of the U-shaped flanges that often retain them. The flanges are made from malleable metals. The use of malleable metals promotes flange thinning at the interface of the flange element and the sealing element. The flanges are particularly susceptible to cracking in the central web portion between the upper and lower legs of the flange. The likelihood of flange failure is increased as the elastic recovery of the disposed fire ring is decreased.
A goal of the present invention is to provide an annular sealing member that is readily deformable during installation to conform to a desired shape. However, the same sealing member also includes excellent strength characteristics to avoid undesirable thermal crushing once installed.